Ultraviolet damage to bacteria and bacteriophage at low temperatures.
The survival of Escherichia coli B/r WP2 (tryptophan-requiring) from ultraviolet irradiation when suspended in 0.067M phosphate buffer (pH 7) has been studied over the temperature range 22 degrees to -269 degrees C. In unfrozen suspensions there was no appreciable change in sensitivity between 22 degrees and -10 degrees C. The sensitivity in the presence of ice progressively increased by a factor of 7 when the temperature was lowered to -79 degrees C. Between -79 degrees and -196 degrees C the sensitivity decreased to less than four times the sensitivity at 22 degrees C and was not appreciably different at -269 degrees C. Evidence from experiments with bacteriophage T1 and E. coli WP2 HCR(-) (a strain unable to excise thymine dimers) indicates that a new, qualitatively different lesion, less amenable to repair, may replace the thymine dimer in E. coli irradiated at -79 degrees C.
D003080:Cold Temperature; D003090:Coliphages / Q000528:radiation effects*; D003470:Culture Media; D004926:Escherichia coli / Q000528:radiation effects*; D005615:Freezing; D066298:In Vitro Techniques; D011831:Radiation Genetics; D013941:Thymine; D014364:Tryptophan / Q000378:metabolism; D014466:Ultraviolet Rays
D003470:Culture Media; D014364:Tryptophan; D013941:Thymine